You Can Fool Mother Nature About Jet Lag

June 07, 1985|By Jane E. Brody, New York Times News Service.

Vacation season is about to begin in earnest, which means that millions of Americans will be jetting across the United States and overseas. That, in turn, means millions of Americans will be starting their time of rest and relaxation, or adventure and excitement, feeling tired and cranky, headachy and out of sorts. It could be days before they feel ``normal`` again.

These people will not be the victims of a disease, but of a condition known as jet lag, the unwitting consequence of our ability to be transported across three or more time zones in less than a day. As more and more people, including scientists and physicians, become frequent fliers to distant lands, the causes of jet lag and ways to counteract it have attracted considerable professional attention. In the last few years, new approaches have been proposed to minimize the effects of jet lag.

What is jet lag?

If we moved from place to place using animal transport, motor vehicles, trains, ships or foot, by the time we reached a distant destination, our bodies would have more or less adapted to changes in the duration of sunlight and darkness: It takes the body about one day to adjust for each time zone crossed.

Many people, however, want to get where they are going quickly, and that means using high-speed jet travel, which allows an insufficient adjustment period.

A flight from the Eastern United States to Europe, for example, could leave us out of sync for as long as six days after landing, or about one-third of the average vacation abroad. For travel to the Far East, the time change throws us off by half a day: when our bodies think it is night, it is day and vice versa. This could mean a two-week period of internal disarray. By the time we are feeling healthy again, it is almost time to go home, and the flight home will force us to make another adjustment in the body clock.

Actually, we have many more than one clock. About 100 biochemical and hormonal rhythms are coordinated by some as-yet unidentified central mechanism. The various rhythms determine when we are alert and when we are sleepy, when we feel hungry, sexy, hot or cold, and when we are most or least athletic, clear-thinking, coordinated, decisive and patient.

These rhythms are not immutable. Rather, they are programmed and can be repeatedly reprogrammed by factors called Zeitgebers (German for time-givers), which are external and internal stimuli that help our bodies reset their clocks. The primary Zeitgeber is the intensity and duration of light. Others include work schedules, food, alcohol, caffeine, exercise, mental stimulation and social activity.

Even if we do nothing purposely to change the body`s sense of day and night, it will automatically readjust as we are exposed to such factors in the new time zone. However, different internal rhythms require varying lengths of time to make the adjustment.

While some can make a three-hour switch in a day, others take as long as seven days. In general, after a trip to Europe or farther, it will take a minimum of two weeks for all body rhythms to become fully synchronized once again.

How far short of normal we feel will vary. Usually, the younger the travelers, the less discomfort experienced and the faster the adaptation to changes in time zones.

Most people have an easier time flying east to west (when they initially will experience a longer day), than west to east (when the first day is cut short), probably because the natural circadian rhythm is really about 25, not 24, hours long; it is easier for us to adjust to the longer day than to the shorter one.

There are a number of time-honored approaches that many people find helpful. If there is enough warning and their schedules permit, travelers can try to preset their biological clock: Determine the number of hours for which one will have to adjust and that many days before, start shifting sleep times and meal times one hour each day. In this way, travelers will arrive at their destinations with their body clocks appropriately calibrated.

Start out well rested and don`t plan demanding activities for the first day away. Take a short nap, if necessary, during the day, but try not to go to bed too early. If sleep seems elusive, try to exercise a little or take a hot bath, but avoid using alcohol, tranquilizers or sleeping pills because these will delay the body`s adjustment.

Drink lots of plain fluids on the plane, since dehydration (the atmosphere aloft can be as dry as a terrestrial desert) aggravates the distress of jet lag. Caffeine, sweetened soft drinks and alcohol compound the problem because they are dehydrating.

Avoid smoking and eating big meals on the plane; these add to fatigue and stress on the body. As often as possible, move around while on the plane. Try some relaxing isometric exercises while seated.